Aeration & sand

coolbrzeSeptember 2, 2008

A friend has a 1/6 acre yard that has a lot of clay in it and water absorption is a problem. There is only a small (~1/4" - 1/2" tops) layer of topsoil in places and grass obviously isn't growing well. I know the best remedy would be to bring in a truckload of topsoil & spread but this is not cost feasible for them.

They mentioned putting sand down then aerating 3 times to get it into the soil/clay/backfill from their house. What do you think about this suggestion and would you recommend a core or spike aerator? In VA temps are in the mid-80s now and it's pretty dry. When is a good time to aerate? Finally, how much & what kind of sand should we put down? Thanks in advance.

I would recommend a core aerator (spike aerators cause more compaction around the hole in clay) and would not recommend the sand. Sand can make clay worse unless you add enough and it takes A LOT of sand to improve things. Instead of sand, I would advise using compost if you can get it in bulk.

From now on, never bag the clippings--always mulch mow. If you've got trees, mulch mow the leaves. If you've got a Starbucks nearby, stop in when you pass it and pick up their grounds for the garden. Other coffee shops and restaurants may save the grounds if you ask, but it's corporate policy for Starbucks. Spread them on the lawn in a thin layer. I don't save them until I have enough to do the whole lawn. I spread them as I get them, picking up where I left off the last time. Don't spread them more than about 1/4 inch deep. The coffee grounds are a mild fertilizer, but the main thing they do for the clay is add organic matter.

Over time, the addition of the organic matter will loosen the clay. The disadvantage of organic matter compared with sand is that sand is a permanent change, but you need to add the organic matter every year. But with organic matter, you can't make things worse as you can with sand.

he does realize that it will take a 50% mix of sand to do what he wishes? if he wants 6" of decent topsoil, then he needs 3" of sand to till in with the clay. and if he has redclay adding sand can be worse since it is already a sandy clay. we use sand around here to get better soil when needed, but how well it works in other areas is up for debate.

Coffee is acidic, but the grounds aren't. I wish they were, because my soil is alkaline. They're actually pretty close to neutral, so they tend to bring both acidic and alkaline soils closer to neutral, albeit slowly.

You need more soil, 1/4 - 1/2 inch of top soil is not good.
Typical contractor move though, to spread a paper thin layer of top soil over terrible sub soil.

I have a different problem, I have 2ft thick layer of moderate clay soil. It has neutral Ph and holds water like you wouldn't believe. I've been adding sand to the clay soil over the last 2-3 years and it is improving the texture of the soil but very slowly.

You will be stunned to find out how much sand is required to cover your lawn to a 1/4 inch depth!!!

I'll typically core aerate and apply sand in spring and fall. No more than 1/4 inch of sand each time followed by rigorous raking. Its interesting to note that the sand has made it way down into the soil and appears to be loosening it quite well. Again, this year, I dug a 6in X 6in test hole at random in an inconspicuous area of my lawn just to see how the aerating is doing. The sand is dispersed into the top 2 inches of the soil quite well considering I have only 6 applications so far. I plan to add some compost next year but no more than 1/2" on the lawn. I'm saving my pennies for that. Core aerating and applying sand is a long term plan. I'm thinking 10 years minimum to change the structure of my soil. I have noticed an increase in earth worm activity over the last year or two. The last two plugs of sod I pulled up were literally peppered with worm holes, we're talking about an earth worm hole every 1 inch apart! Those guys are helping me to change the soil more than I could ever do with a core aerator.

I know you said its not "cost feasable" for your friend, but trying to work with 1/4 - 1/2 inch of top soil is a tough battle before you've done anything. The grass will not do well in those conditions.

This year, I core aerated on 1st August prior to fertilising and right now the lawn is fantastic, dark rich green and thicker than it has ever been. I figured coring the soil prior to fertilising would allow the fertiliser easy access to the roots..... it worked.

See if your friend can scrounge some top soil from local contractors or neighbors? Local farmer might be able to help in exchange for favours (free labour for a weekend kind of thing)...

Coffee grounds!? Awesome, I'm going to start doing that... I use a coffee maker called a "Toddy" which uses one pound of coffee at a time to make a concentrate and I'm always left with a ton of grounds (well I guess a pound actually, heh) that go in the trash. Not any more!

Cost and workwise your friend would be better off to core aerate 2x year and sling 20 bags of the cheap manure/compost from Lowes around the yard each time. He will have earthworms in less than a year that will soften up that soil a bunch. Adding organic fertilizers and leaf mulching helps a lot too. All of the above is better than adding sand.